Patent document 1 discloses an internal combustion engine (hereinafter referred to as “variable compression ratio internal combustion engine”) provided with a variable compression ratio mechanism capable of changing an engine compression ratio in accordance with a rotational position of a control shaft. A speed reducing mechanism is provided between the control shaft and an actuator such as a motor that drives the control shaft. A rotation shaft, which is linked through a lever to the control shaft, is provided in the speed reducing mechanism. For example, the rotation shaft is rotatably supported in a housing fixed to an engine body.